General characteristics. Mushrooms are a kingdom of living organisms that combine the characteristics of plants and animals.
Brings them closer to plants. 1) the presence of a well-defined cell wall; 2) immobility in a vegetative state; 3) reproduction by spores; 4) ability to synthesize vitamins; 5) absorption of food by absorption (adsorption). Common to animals is: 1) heterotrophy; 2) the presence of chitin in the cell wall, characteristic of the exoskeleton of arthropods; 3) absence of chloroplasts and photosynthetic pigments in the cells; 4) accumulation of glycogen as a reserve substance; 5) formation and release of a metabolic product - urea. These structural features and vital functions of fungi allow us to consider them one of the most ancient groups of eukaryotic organisms that do not have a direct evolutionary connection with plants, as previously thought. Fungi and plants arose independently of the different forms of microorganisms that lived in water.
More than 100 thousand species of mushrooms are known, and it is assumed that the real number is much higher - 250-300 thousand or more. More than a thousand new species are described every year around the world. The vast majority of them live on land, and they are found almost everywhere where life can exist. It is estimated that in the forest litter 78-90% of the biomass of all microorganisms is accounted for by the fungal mass (approximately 5 t/ha).
The structure of mushrooms. The vegetative body of the vast majority of fungal species is mycelium, or mycelium, consisting of thin, colorless (sometimes slightly colored) threads, or hyphae, with unlimited growth and lateral branching.
The mycelium usually differentiates into two functionally distinct parts: substrate, serving for attachment to the substrate, absorption and transportation of water and substances dissolved in it, and air, rising above the substrate and forming reproductive organs.
Reproduction. Fungi reproduce asexually and sexually. Asexual reproduction occurs in parts of the mycelium or individual cells, which give rise to a new mycelium. Yeasts reproduce by budding.
Asexual reproduction can also be carried out through endo- and exogenous spores. Endogenous spores are formed inside specialized cells - in sporangia. Exogenous spores, or conidia, arise openly at the ends of special specialized mycelial outgrowths called conidiophores. Once in favorable conditions, the spore germinates and a new mycelium is formed from it.
Sexual reproduction in fungi is especially diverse. In some groups of fungi, the sexual process occurs by the fusion of the contents of two cells at the ends of the hyphae. In marsupial fungi, there is a fusion of the contents of the antheridium and the female organ of sexual reproduction (archegonium), not differentiated into gametes, and in basidiomycetes there is a fusion of the contents of two vegetative cells, in which outgrowths or anastomoses are often formed between them.
Mushroom nutrition. For the normal functioning of mushrooms, ready-made organic nutrients, mineral salts, and vitamins are needed. Some mushrooms only use ready-made compounds. Others can synthesize most of the nutrients themselves, but require some additional nutritional components.
Mushrooms absorb nutrients, absorbing them throughout the surface of the body.
Saprophytic fungi secrete a variety of digestive enzymes (from the Latin fermentum - “ferment”), destroying complex organic substances to simple inorganic ones, therefore they actively participate in the cycle of substances. For example, green mold - the penicillium fungus - grows on bread, on raw skin, and rotting fruit.
Predatory fungi from the family of zoopagal fungi catch nematode worms and mobile amoebae living in the soil, using their sticky thickenings at the ends of the hyphae or special trap loops, which immediately swell and contract when touched. An animal caught in this way, for example a nematode, is firmly held (Fig. 123). Threads of hyphae quickly grow into the victim. They secrete enzymes into it, and then the fungus sucks out the contents of the nematode’s body.
Symbiont fungi are widespread in nature, cohabiting with different types of plants (higher and lower). Fungi form a special cohabitation with higher plants - the so-called fungal root, or mycorrhiza, and with lower plants and cyanobacteria - lichen.
CLASSIFICATION OF MUSHROOMS
Based on the types of sexual process, the nature of flagellation in motile stages (zoospores and gametes), the development of sexual spores and other characteristics, fungi are divided into main classes.
Chytridiomycetes. The mycelium of these fungi is poorly developed or absent. Zoospores and gametes with one posterior flagellum.
Hyphochytriomycetes. The mycelium is poorly developed or absent. Zoospores and gametes with one anterior feathery flagellum.
Oomycetes. The mycelium is well developed. Non-cellular. Zoospores with two unequal flagella - pinnate and whip-shaped. The sexual process is oogamy.
Zygomycetes. The mycelium is well developed and, with few exceptions, acellular. There are no moving stages. Asexual reproduction in most species is by immobile sporangiespores produced inside sporangia. Less often - with the formation of conidia. The sexual process is zygogamy (the fusion of two gametangia, the structure of which is clearly distinguishable from the vegetative hyphae on which they are formed).
Ascomycetes. The mycelium is well developed and cellular. There are no moving stages. Asexual reproduction using conidia. The sexual process is gametangiogamy. Spores of sexual reproduction are formed endogenously, in bags.
Basidiomycetes . The mycelium is well developed, cellular (usually dikaryonic). There are no moving stages. Asexual reproduction using conidia. The sexual process is somatogamy. Sexual spores are formed exogenously, on basidia.
Deuteromycetes, or imperfect fungi (Deuteromycetes, Fungi imperfecti). The mycelium is well developed and cellular. Reproduction is only vegetative and asexual, in the latter case with the help of conidia. There is no sexual process. The group is in its infancy and is related in origin primarily to the two previous classes.
Classification involves the division of fungi into specific, clearly demarcated groups - the so-called taxa. These groups are distributed according to the principle of hierarchy in a clearly ordered system. In other words, they are mutually subordinate and located at different levels – ranks. Currently, fungi are a separate kingdom, but during the formation of taxonomy they were classified as plants. This explains the fact that the fungal system contains the same taxa as plants: department, class, order, family, genus, species.
Signs of mushrooms
When dividing into groups, the characteristics of fungi are identified that unite or separate them (taxonomic characteristics). The choice determines what basic features the created system will have, whether it will express only the external similarity of organisms or indicate their actual relationship. The progressive development of mycology has made it possible to build a fungal system based on a set of characteristics. These taxonomic characters must satisfy the basic requirements - to be evolutionarily constant and determine the related relationships of fungi. The main taxonomic characters that are used in the taxonomy of fungi, as well as other groups of living organisms, are morphological. These are structural features, including ultrastructure, studied only using an electron microscope. But the complex of such characters in many groups of fungi is often small, and they may be similar in unrelated groups growing under the same environmental conditions. Therefore, recently other complexes of characteristics have been used in the taxonomy of fungi - biochemical (type of metabolism, formation of certain metabolic products, etc.), environmental, genetic, etc. In recent years, great importance has been attached to such a feature as the structure of nucleic acids, in particular DNA, that is, the structure of genetic material.
The taxonomy of any group is based on such an important taxon as the species. When describing species, the limits of variation in their characteristics are always indicated. Species are grouped into genera, which, in turn, are grouped into families, families into orders, orders into classes, classes into divisions, and divisions into the kingdom of fungi.
The fungal kingdom is divided into two divisions:
1. Oomikota.
2. Eumikota (real mushrooms).
Classes are differentiated based on the type of reproductive organs and a number of structural features of the vegetative body of fungi. Only two classes belong to the department Oomycota (oomycetes and hyphochytriomycetes). They differ in the number of flagella and the composition of cell membranes. The vast majority of fungi (96%) belong to the department Eumycota, in which five classes are distinguished (chytridiomycetes, zygomycetes, ascomycetes, basidiomycetes, deuteromycetes). The so-called macromycetes - fungi with fruiting bodies of large sizes, clearly visible without a microscope - are representatives of two classes of fungi - basidiomycetes and ascomycetes.
№ 6 Morphology of fungi
Mushrooms belong to the kingdom Fungi (Mycetes, Mycota ). These are multicellular or unicellular non-photosynthetic (chlorophyll-free) eukaryotic microorganisms with a cell wall.
Mushrooms have a nucleus with a nuclear envelope, cytoplasm with organelles, a cytoplasmic membrane and a multilayered, rigid cell wall consisting of several types of polysaccharides, as well as proteins, lipids, etc. Some fungi form a capsule. The cytoplasmic membrane contains glycoproteins, phospholipids and ergosterols. Fungi are gram-positive microbes, vegetative cells are non-acid-resistant.
Mushrooms consist of long thin threads (hyphae) intertwined into mycelium, or mycelium. The hyphae of lower fungi - phycomycetes - do not have partitions. In higher fungi - eumycetes - the hyphae are separated by septa; their mycelium is multicellular.
There are hyphal and yeast forms of fungi.
Hyphal(mold) fungi form branching thin threads (hyphae) intertwined into mycelium, or mycelium (mold). Hyphae growing into the nutrient substrate are called vegetative hyphae (responsible for feeding the fungus), and those growing above the surface of the substrate are called aerial or reproductive hyphae (responsible for asexual reproduction).
Hyphae lower mushrooms do not have partitions. They are represented by multinucleated cells and are called coenocytic.
Hyphae higher mushrooms are separated by partitions, or septa with holes.
YeastFungi (yeasts) mainly have the appearance of individual oval cells (unicellular fungi). According to the type of sexual reproduction, they are distributed among higher fungi - ascomycetes and basidiomycetes. When reproducing asexually, yeast buds or divides, resulting in single-celled growth. They can form pseudohyphae and false mycelium (pseudomycelium) in the form of chains of elongated cells - “sausages”. Fungi that are similar to yeast, but do not have a sexual method of reproduction, are called yeast-like. They reproduce only asexually - by budding or fission.
Mushrooms multiplyspores by sexual and asexual means, as well as by vegetative means (budding or fragmentation of hyphae). Fungi that reproduce sexually and asexually are classified as perfect. Imperfect fungi are those in which sexual reproduction is absent or has not yet been described. Asexual reproduction is carried out in fungi with the help of endogenous spores that mature inside a round structure - sporangium, and exogenous spores - conidia, which form at the tips of fruiting hyphae.
Types of mushrooms.There are 3 types of fungi that have a sexual method of reproduction (the so-called perfect fungi): zygomycetes ( Zygomycota), ascomycetes (Ascomycota ) and basidiomycetes ( Basidiomycota ). Separately, a conditional, formal type/group of fungi is distinguished - deuteromycetes ( Deiteromycota ), which have only asexual reproduction (the so-called imperfect mushrooms).
Mushrooms were classified as lower plants until the end of the 20th century. In 1970, they were finally separated into a separate kingdom, Mushrooms, because have a number of characteristics that distinguish them from plants and bring them closer to animals.
general characteristics
The kingdom fungi are unicellular and multicellular organisms. Currently, taxonomists have counted more than 100 thousand species of fungi.
Fungi are heterotrophic organisms that do not have chlorophyll. They occupy an intermediate position between animals and plants, as they are characterized by a number of properties that bring them closer to animals and plants.
Common signs of fungi and animals:
- The cell membrane contains chitin;
- they accumulate glycogen rather than starch as a reserve product;
- as a result of the exchange, urea is formed;
- absence of chloroplasts and photosynthetic pigments;
General characteristics of mushrooms and plants:
- Unlimited growth;
- absorptive nutrition, i.e. not swallowing food, but absorption;
- the presence of a pronounced cell wall;
- reproduction by spores;
- immobility;
- ability to synthesize vitamins.
Mushroom nutrition
Many species of the kingdom of Fungi live in cohabitation (symbiosis) with algae and higher plants. The mutually beneficial cohabitation of fungal mycelium with the roots of higher plants forms mycorrhiza (for example, boletus with birch, boletus with aspen).
Many higher plants (trees, durum wheat, etc.) cannot grow normally without mycorrhiza. Fungi receive oxygen, root secretions, and compounds that do not contain nitrogen from higher plants. Fungi “help” higher plants absorb hard-to-reach substances from humus, activating the activity of enzymes in higher plants, promote carbohydrate metabolism, fix free nitrogen, which is used in a number of compounds by higher plants, provide them with growth substances, vitamins, etc.
The kingdom Mushrooms are conventionally divided into lower and higher. The basis of the vegetative body of mushrooms is the mycelium, or mycelium. Mycelium consists of thin threads, or hyphae, similar to fluff. These threads are located inside the substrate on which the fungus lives.
Most often, the mycelium occupies a large surface. Through mycelium Nutrients are absorbed osmotically. The mycelium of lower fungi is either divided into cells or there are no intercellular partitions.
Mono- or multinucleated fungal cells are in most cases covered with a thin cell membrane. Underneath it is a cytoplasmic membrane that envelops the cytoplasm.
The fungal cell contains enzymes, proteins and organelles (lysosomes) in which proteins are broken down by proteolytic enzymes. Mitochondria are similar to those of higher plants. Vacuoles contain reserve nutrients: glycogen, lipids, fatty acids, fats, etc.
Edible mushrooms contain many vitamins and mineral salts. Approximately 50% of the dry mass of mushrooms is nitrogenous substances, of which proteins account for about 30%.
Fungi reproduce asexually:
- Specialized cells - spores;
- vegetatively - parts of mycelium, budding.
The process of sporulation may be preceded by the sexual process, which is very diverse in fungi. A zygote can be formed as a result of the fusion of somatic cells specialized for gametes and germ cells - gametes (formed in the genital organs - gametangia). The resulting zygote germinates immediately or after a period of dormancy and gives rise to hyphae with sexual sporulation organs, in which spores are formed.
Spores of various fungi are spread by insects, various animals, humans and air currents.
The importance of mushrooms in nature and human life
Molds settle on food, soil, vegetables and fruits. They cause spoilage of benign products (bread, vegetables, berries, fruits, etc.). Most of these fungi are saprophytes. However, some molds are causative agents of infectious diseases in humans, animals and plants. For example, the fungus trichophyton causes ringworm in humans and animals.
Everyone is well aware of the single-celled fungus mucor, or white mold, which settles on vegetables, bread and horse manure. Initially, white mold has a fluffy coating, and over time it turns black, as rounded heads (sporangia) are formed on the mycelium, in which a huge number of dark-colored spores are formed.
Antibiotics are obtained from a number of mold genera (penicillin, aspergillus).
Molds are divided into five classes, mainly based on their reproduction characteristics.
1. Class Archimycetes (Archimycetes). The most primitive mushrooms, which have no mycelium at all or are underdeveloped. Asexual reproduction is carried out by motile zoospores.
Another fungus causes potato cancer. Its spores overwinter in the soil and in the spring they germinate into motile zoospores that infect young plants.
2. Class Phycomycetes (phycomycetes). This includes molds with well-developed mycelium, almost all nonseptate. They reproduce sexually or vegetatively. Spores (in the first case, zoospores or zygospores, in the second, motile zoospores with two flagella) are formed in sporangia. The class of phycomycetes includes mushrooms of the genus Mukor, widespread in nature, living in the soil and on various food products. They reproduce with the help of spores formed in sporangia on special hyphae - sporangiophores - of various shapes.
Rice. 8. Capitate mold of the genus Mukor: a - sporangia with spores; b - disputes; c - mycelium.
3. Class Ascomycetes (ascomycetes, or marsupial fungi). Molds of different structure and properties, having unicellular or multicellular mycelium. Asexual reproduction is carried out by conidia, sexual reproduction is carried out by spores in bags (ascospores).
Representatives of filamentous marsupial fungi are fungi of the genus Endomyces, the mycelium of which often disintegrates into individual cells. Cells reproduce by budding. Yeasts belong to marsupial fungi that do not form mycelium.
Aspergillus (club mold) often found on damaged grain, in hops, in damp rooms, on damp containers and on the remains of sugar-containing liquids.
Young conidia are light green in color, then darken and become gray-brown. Conidiophores are straight with spherical swellings at the ends. On the swellings, cells grow radially - sterigmata, shaped like bottles (Fig. 9, a). Conidia develop and release from the sterigmata in large numbers. Sometimes they completely cover the swelling of the conidiophore.
Rice. 9. Marsupial fungi (ascomycetes): a - Aspergillus: 1 - conidia; 2 - mycelium with conidiophores of different ages; 3 - conidiophore; 4 - bifurcated sterigmata; b - Penicillium: 1 - conidia; 2 - germinating conidia and mycelium development; 3 - development of the conidiophore; 4 - various conidiophores with conidia.
Penicillium(Fig. 9, b) - green brush mold. For all species of the genus Penicillium, a common feature is the color, which at the beginning of development is white, then gray-green and finally gray-brown.
Multicellular conidiophores of the Penicillium mold are brush-shaped and end in branched sterigmata. At their ends, like rosary beads, there are conidia. As the conidia mature, they fall off, forming bluish dust on surrounding objects. This mold is ubiquitous and appears on all food products in the presence of moisture. Conidia of Penicillium fungi are constantly present in the air, on fruits, grains (especially crushed grains), malt, etc.
Some species are used to obtain a medicinal drug - the antibiotic penicillin.
Some types of Fusarium cause spoilage of potatoes (dry rot disease). The Botrytis mushroom causes spoilage of onions, cabbage, carrots, tomatoes, and diseases of berries. Alternaria attacks root crops during storage (black rot disease). The Oidium mushroom spoils pickled vegetables and fermented milk products, pressed yeast, forming a white velvety film on the surface. Some Fusariums also cause heart rot in beets. Black spots appear on food products (butter, cheese, meat, eggs), which leads to their spoilage.
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